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Americans have been commemorating the Dec. 7, 1941, Japanese attack on Pearl Harbor for 71 years now. That’s as it should be.

It was more than a historic day, it was a monumental event, one that brought the United States into World War II. Though America suffered other defeats, Pearl Harbor marked the beginning of the end of the Empire of Japan and Hitler’s Third Reich and transformed the United States into a superpower.

We pause to remember, as we should, the more than 2,400 lives lost that day. But when we contemplate Pearl Harbor from the distance of roughly a lifetime, we also honor the generation whose members died there and in countless battlefields in what was nothing less than an epic struggle between the forces of freedom and the forces of tyranny. That generation’s triumph in World War II isn’t the only reason it’s called the Greatest Generation, but that conflict was a test of mettle unlike any since.

In the 21st century, it’s difficult to contemplate Pearl Harbor without also considering the terrorist attacks of Sept. 11, 2001. It, too, was a surprise attack that shattered a peaceful morning. Its death toll was greater, and unlike Pearl Harbor, most victims were civilians. It, too, shocked and outraged the nation and was forever etched into the memories of all who watched in horror as the Twin Towers crumbled. And like Pearl Harbor, 9/11 led us to war.

But the entire nation didn’t go to war, as occurred in 1941. Far from it. Despite President George W. Bush’s stirring words atop the rubble of Ground Zero, able-bodied young people didn’t flock to recruiting offices as they did after Pearl Harbor. And unlike the sacrifices expected as part of the earlier war effort, next to nothing was — or has been — asked of civilians after 9/11. Civilians thank soldiers, of course, but we wouldn’t think of rationing gas or doing without certain foods and other commodities; we’d be as likely to complain about shortages or prices. That’s partly, if not primarily, because other than the tiny fraction of Americans doing the fighting and their families, few Americans feel as if we’re at war.

Rare was the American who was under any such illusion after Pearl Harbor. Americans — in or out of uniform — knew what needed to be done and did it. They knew their cause was a noble one, and knew that achieving it would require great — and sometimes ultimate — sacrifices.

Those sacrifices began 71 years ago today, and they can never be forgotten.